Field of the Invention
The present invention relates to a recording medium suitable for ink-jet systems, and, more particularly, to a recording medium whose printing surface and image-viewing surface are in an obverse and reverse relationship, and which can obtain recorded images superior in gloss and storage stability without effecting a post-treatment such as laminating.
Related Background Art
Hitherto used as recording mediums suited for ink-jet recording systems, particularly for full color recording, are ink-jet papers comprising a porous layer formed by coating pigments such as silica on a paper surface, and ink-jet OHP (overhead projector) films comprising a plastic film surface coated with resins absorptive of inks by dissolution or swelling.
The above described ink-jet paper, in which the absorption of inks is effected by its porous layer, absorb inks speedily and is therefore suited for making images multicolored and for high speed printing, advantageously. On the other hand, however, since images are viewed also from the same porous layer side as the printing surface, it is so constituted that recording agents are forced to remain as much as possible on the surface of an absorbing layer, thus having the disadvantage that it is inferior in the durability such as water resistance and abrasion resistance and the storage stability of images, and the disadvantages such that there can be obtained no glossy recorded images.
Glossy images can be obtained in the recording mediums of the type in which the inks are absorbed by dissolution or swelling of resins like the ink-jet OHP films, but inks are so slowly absorbed and fixed that there are also problems that staining or feathering due to the transfer of images, and also non-uniformity of image density called beading caused by irregular migration of inks tend to occur in the high speed printing or multicolor printing to make it difficult to obtain sharp and beautiful images.
On the other hand, Japanese Patent Laid-open Publications No. 136480/1983, No. 136481/1983, No. 197285/1986, etc. contain disclosures relating to ink-jet recording mediums of the type that a porous ink absorbing layer is provided on a transparent support, the recording is performed from the porous ink absorbing layer side according to the ink-jet system, and images are viewed from the transparent support side.
The recording mediums of this type are advantageous as the various performances such as water resistance and abrasion resistance have been sufficiently settled, and yet inks can be speedily absorbed, highly glossy images can be obtained, and beading can be prevented from occurring. However, when printing is performed on the recording mediums of this type according to the ink-jet system, there has been a disadvantage that even through the image-viewing surface is the transparent support side, actually the image density at the viewing surface side becomes lower than the image density at the printing surface side.
To settle this problem, the present inventors developed previously a recording medium such that the image density of the viewing surface may be raised higher that that of the printing surface by providing an ink-retaining layer between a porous ink-transporting layer and a transparent substrate. Further the porous ink-transporting layer absorbs inks by itself as little as possible and has through-holes (EP No. 227 254 A2).
However, also in the recording medium according to this prior invention, it is difficult to obtain the porous ink-transporting layer that allows all of the inks to penetrate into the ink-retaining layer and does not allow any ink to remain at all in the former, actually leading to the result that ink components always more or less remain in the porous ink-transporting layer. For this reason, when the records obtained by performing recording on the above recording medium according to the ink-jet system are stored for a long period of time or stored under the condition of high humidity, there has arisen the problem that a colorant in an ink migrates by diffusion over the surfaces of pores in the porous ink-transporting layer to cause feathering of images.
In order to prevent such feathering of images after storage, it is known to add to the porous layer a material having the property of fixing the colorant in the ink in the case of the above-mentioned conventional ink-jet coat paper or the like.
However, in the above recording medium of the prior invention made by the present inventors, the ink-applying surface and the image-viewing surface are in an obverse and reverse relationship, and a porous ink-transporting layer that may not allow the greater part of colorant to remain but has good liquid permeability is provided for the purpose of increasing the image density on the viewing surface. Accordingly, incorporation of the colorant-fixing material as mentioned above into this porous ink-transporting layer has been an idea that has not been hitherto considered since it decreases not only the liquid permeability of the ink-transporting layer but also the ink absorbing ability of the whole recording medium to lower the image density on the viewing surface.